Validation of volume kinetic analysis of glucose 2.5% solution given by intravenous infusion

Background. The distribution and elimination of glucose solutions can be analysed by means of a volume kinetic model, but the ability of the model to predict plasma dilution ('model linearity') has not been evaluated. Methods. Six male volunteers received four separate infusions of glucose 2.5%: 10 ml kg(-1) and 15 ml kg(-1) over 30 min, and 15 ml kg(-1) and 25 ml kg(-1) over 60 min. The kinetic model was fitted to measurements of plasma glucose concentration and haemodilution. Results. The mean volume of distribution for the glucose was 9.2 (SEM 0.4) litres while the infused fluid expanded a central body fluid space (V-1) of 3.1 (0.3) litres. Increasing the amount of infused fluid, but not the infusion rate, resulted in a proportional increase in the area under the curve for plasma glucose and plasma dilution, the only confounder being glycosuria. The bias of computer simulation was slightly increased by rebound hypoglycaemia, which could occur with the highest infusion rates, but the accuracy was almost identical regardless of whether the kinetic parameters from all 24 experiments or from any of the subgroups were used. Conclusion. The volume kinetic model for glucose 2.5% is linear and can therefore be used for computer simulation as long as marked glycosuria does not occur.